Wind-sand tunnel experiment on the windblown sand transport and sedimentation over a two-dimensional sinusoidal hill

Turbulent wind flow over hilly terrains has been extensively investigated in the scientific literature and main findings have been included in technical standards. In particular, turbulent wind flow over nominally two-dimensional hills is often adopted as a benchmark to investigate wind turbine siting, estimate wind loading, and dispersion of particles transported by the wind, such as atmospheric pollutants, wind-driven rain, windblown snow. Windblown sand transport affects human-built structures and natural ecosystems in sandy desert and coastal regions, such as transport infrastructures and coastal sand dunes. Windblown sand transport taking place around any kind of obstacle is rarely in equilibrium conditions. As a result, the modelling of windblown sand transport over complex orographies is fundamental, even if seldomly investigated. In this study, the authors present a wind-sand tunnel test campaign carried out on a nominally two-dimensional sinusoidal hill. A first test is carried out on a flat sand fetch without any obstacle to assess sand transport in open field conditions. Then, a second test is carried out on the hill model to assess the sand flux overcoming the hill and the morphodynamic evolution of the sand sedimenting over its upwind slope. Finally, obtained results are condensed into a dimensionless parameter describing its sedimentation capability and compared with values resulting from other nominally two-dimensional obstacles from the literature

Wind-sand tunnel testing of surface-mounted obstacles: Similarity requirements and a case study on a Sand Mitigation Measure

Windblown sand flow interacts with a number of surface-mounted human-built obstacles. The wind-sand flow perturbation and resulting morphodynamic response of the sand bed cannot be assessed in analytical terms. Therefore, wind-sand tunnel studies around scale physical models are often carried out. They should be driven by physical similarity theory based on dimensionless numbers referred to the whole multiphase and multiscale flow. However, similarity requirements cannot be fully satisfied under typical testing conditions and attention should be paid on the extent of the similarity relaxation. In this study, the background of wind-sand tunnel testing of surface-mounted obstacles is recalled by reviewing wind tunnel setups and similarity requirements. Then, a wind-sand tunnel campaign on a Sand Mitigation Measure is described and critically discussed. The setup dimensionless numbers are compared with statistics on those of past studies. The inescapable relaxation of similarity requirements is motivated by the test goals. The time evolution towards in-equilibrium conditions of both sand bed morphodynamics and sand transport is discussed. Finally, the results of engineering interest are described: the Sand Mitigation Measure sand trapping performance is assessed in dimensionless terms through the measurements of the incoming and outgoing sand concentration in air

Sensitivity analysis on turbulence models for the ABL in complex terrain

Análisis de sensibilidad de modelos de turbulencia para un modelo CFD de viento aplicados a un emplazamiento en terreno complejo. Validación con datos de viento y turbulencia registrados a 3 alturas en 3 torres de medida

Predictors associated with low-risk women's pre-labour intention for intrapartum pain relief: a cross-sectional study

Background: Pregnant women have preferences about how they intend to manage labour pain. Unmet intentions can result in negative emotions and/or birth experiences. Objective: To examine the antenatal level of intention for intrapartum pain relief and the factors that might predict this intention. Design: A cross-sectional online survey-based study. Setting and participants: 414 healthy pregnant women in the Netherlands, predominantly receiving antenatal care from the community-based midwife who were recruited via maternity healthcare professionals and social media platforms. Methods: The attitude towards intrapartum pain relief was measured with the Labour Pain Relief Attitude Questionnaire for pregnant women. Personality traits with the HEXACO-60 questionnaire, general psychological health with the Mental Health Inventory-5 and labour and birth anxiety with the Tilburg Pregnancy Distress Scale. Multiple linear regression was performed with the intention for pain relief as the dependant variable. Results: The obstetrician as birth companion (p<.001), the perception that because of the impact of pregnancy on the woman’s body, using pain relief during labour is self-evident (p<.001), feeling convinced that pain relief contributes to self-confidence during labour (p=.023), and fear of the forthcoming birth (p=.003) predicted women were more likely to use pain relief. The midwife as birth companion (p=.047) and considering the partner in requesting pain relief (p=.045) predicted women were less likely to use pain relief. Conclusion: Understanding the reasons predicting women’s intention of pain management during labour, provides insight in low-risk women’s supportive needs prior to labour and are worth paying attention to during the antenatal perio.

Predicting deformation-induced polymer-steel interface roughening and failure

A novel integrated framework is presented for the prediction of deformation-induced interface roughening and failure in polymer-coated steels. Crystal plasticity is employed to predict the change in steel surface roughness in-situ. The steel substrate is coated with a thin polymer layer and the polymer-steel interface is modeled using an exponential cohesive zone law. Uniaxial tensile simulations are performed and the results show that the predicted roughness increases with the applied deformation. The local changes in the steel surface profile result in initiation and growth of local interface failure. Furthermore, a compression simulation shows that the roughening rate of the steel is increased compared to tension, with an increase in the predicted interface damage as a result. The presented framework thus allows for a detailed numerical study of the initiation and growth of interface damage in polymer-coated steels during applied deformation. The incorporation of the crystal plasticity model to predict the changes in the steel surface profile complements the cumbersome measurements of detailed experimental displacement fields that accompany deformation-induced roughening and thus enables the analysis of deformation processes where measuring the steel surface profile is difficult if not impossible, e.g. industrial forming processes such as deep-drawing

Excerpt of a Letter from A. J. Van Beeck Calkoen to G. Groen van Prinsterer

An excerpt of a letter of A. J. Van Beeck Calkoen to G. Groen van Prinsterer about the need for special schools so that religious instruction can be given.https://digitalcommons.hope.edu/vrp_1840s/1062/thumbnail.jp

Numerical CFD modelling of non-neutral atmospheric boundary layers for offshore wind resource assessment based on Monin-Obukhov theory

The presented works aim at proposing a methodology for the simulation of offshore wind conditions using CFD. The main objective is the development of a numerical model for the characterization of atmospheric boundary layers of different stability levels, as the most important issue in offshore wind resource assessment. Based on Monin-Obukhov theory, the steady k-ε Standard turbulence model is modified to take into account thermal stratification in the surface layer. The validity of Monin-Obukhov theory in offshore conditions is discussed with an analysis of a three day episode at FINO-1 platform

Olfactory cues of large carnivores modify red deer behavior and browsing intensity

This study examined the effect of perceived predation risk imposed by lynx (Lynx lynx) and wolf (Canis lupus) on red deer (Cervus elaphus) foraging behavior under experimental conditions. We hypothesized that in response to large carnivore scent red deer would increase their vigilance, although reducing the frequency and duration of visits to foraging sites. Consequently, browsing intensity on tree saplings was expected to decrease, whereas a higher proportion of more preferred species was expected to be browsed to compensate for higher foraging costs. We expected stronger responses towards the ambush predator lynx, compared with the cursorial predator wolf. These hypotheses were tested in a cafeteria experiment conducted within three red deer enclosures, each containing four experimental plots with olfactory cues of wolf, lynx, cow, and water as control. On each plot, a camera trap was placed and browsing intensity was measured for one consecutive week, repeated three times. Red deer reduced their visitation duration and browsing intensity on plots with large carnivore scent. Despite red deer showing a clear preference for certain tree species, the presence of large carnivore scent did not change selectivity towards different tree species. Contrary to our hypothesis, we found more pronounced effects of wolf (cursorial) compared with lynx (ambush). This study is the first to experimentally assess the perceived risk effects on the red deer foraging behavior of large carnivores differing in hunting modes. Our findings provide insights into the role of olfactory cues in predator-prey interactions and how they can modify fine-scale herbivore-plant interactions.publishedVersio